Spain will be the first to go

"Why will Spain exit the eurozone? Because you can’t squeeze blood from a stone. With a 24% unemployment rate that is rising, and over half of the young people unemployed, no politician in his right mind—especially a nationalist—will decide that even more austerity is the cure for the disease. One thing is cutting off the fat—it’s quite another to be cutting to the bone.

For Rajoy and de Guindos, it will be simpler to exit the eurozone, go back to the peseta, and devalue by 20% to 30% right off.

It is always easier for a politician to cut expenditures via devaluation than via nominal spending cuts. Since the Eurocrats won’t allow a 20-30% devaluation of the euro, and since Spain cannot really cut any more or find any more money in the bond markets, then the only thing left for it to do is devalue a currency that it controls:

The New Peseta: Coming to Spain before the end of the year."
--http://gonzalolira.blogspot.com/2012/04/spain-will-exit-eurozone-firstthis-year.html 

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"Fourth, it [Spain] is politically secure, with the self-confidence that comes from that.  Greece wants to stay in the euro because it locks it into Europe, Ireland because it separates it from Britain, Germany because Europe represents a break with its troubled past, France because the euro boosts its prestige in the world.  Spain has none of those issues and can leave if the euro is not working for it.
Fifth, it has bigger horizons as it is able to look outwards to booming Latin America for markets rather than look inwards to flagging Europe."
--http://www.ocnus.net/artman2/publish/Business_1/Why-Spain-Could-Jump-Queue-and-be-First-to-Leave-the-Euro.shtml